The present invention relates generally to ink-jet printing and, more specifically to a method and mechanism for cleaning a belt used in the transport of print media through a printing zone.
The art of ink-jet technology is relatively well developed. Commercial products such as computer printers, graphics plotters, copiers, and facsimile machines employ ink-jet technology for producing hard copy. The basics of this technology are disclosed, for example, in various articles in the Hewlett-Packard Journal, Vol. 36, No. 5 (May 1985), Vol. 39, No. 4 (August 1988), Vol. 39, No. 5 (October 1988), Vol. 43, No. 4 (August 1992), Vol. 43, No. 6 (December 1992) and Vol. 45, No. 1 (February 1994) editions. Ink-jet devices are also described by W. J. Lloyd and H. T. Taub in Output Hardcopy [sic] Devices, chapter 13 (Ed. R. C. Durbeck and S. Sherr, Academic Press, San Diego, 1988).
FIG. 1 (Prior Art) is a schematic depiction of an ink-jet hard copy apparatus 10. A writing instrument 12 is provided with a printhead 14 having drop generators including nozzles for ejecting ink droplets onto an adjacently positioned print medium, e.g., a sheet of paper 16, in the apparatus' printing zone 34. An endless-loop belt 32 is one type of known manner printing zone input-output paper transport. A motor 33 having a drive shaft 30 is used to drive a gear train 35 coupled to a belt pulley 38 mounted on an fixed axle 39. A biased idler wheel 40 provides appropriate tensioning of the belt 32. The belt rides over a platen 36 in the print zone 34; the platen is described in detail hereinafter, but is associated with a known manner vacuum induction system 37. The paper sheet 16 is picked from an input supply (not shown) and its leading edge 54 is delivered to a guide 50, 52 where a pinch wheel 42 in contact with the belt 32 takes over and acts to transport the paper sheet 16 through the printing zone 34 (the paper path is represented by arrow 31). Downstream of the printing zone 34, an output roller 44 in contact with the belt 32 receives the leading edge 54 of the paper sheet 16 and continues the paper transport until the trailing edge 55 of the now printed page is released. The carriage scanning axis is conventionally designated the x-axis, the print media transit axis is designated the y-axis, and the printhead firing direction is designated the z-axis. For convenience in describing the art and the present invention, all types of ink-jet hard copy apparatus are sometimes hereinafter referred to as “printers;” all types, sizes, and compositions of print media—including non-traditional printing media such as polymeric transparencies, cloth fabric, mylar, and the like—are also referred to simply as “paper;” all compositions of colorants are sometimes referred to as “ink;” and all embodiments of an ink-jet writing instruments are simply referred to as a “pen;” no limitation on the scope of the invention is intended nor should any be implied.
During printing operations, ink deposits or aerosol mixtures of ink and paper dust collect on the belt and platen. Once on the belt, ink begins transferring onto subsequent sheets as well as internal components of the print mechanism. This can cause print defects and unattractive splotches on the reverse side of the print. Thus, there is a need for paper transport belt cleaning mechanisms.